Also, Pentium 4/D are members of the "NetBurst" family of Intel processors.. even if the bug you're experiencing is discovered, the performance of OpenBSD isn't all that great on them.

Intel abandoned this "ground up" redesign of their x86 family due to the performance issues (..cache,soft interrupts,certain instructions), and went back to the P6 architecture (..Pro/PII/PIII) with their new "Core" processors.

If you do wish to use OpenBSD on this system, you should be aware of this.

Also of note, Pentium D does support i386.. if you were unaware of this, you may wish to try OpenBSD/i386, this is on CD1.